Depiction in Equestria Girls

The Dazzlings are first seen in a cafe at the beginning of the film, feeding on the negativity caused by its patrons. There they witness a blast of Equestrianmagic coming from Canterlot High School and decide to exploit it to get everyone in the human world to adore them.

Upon enrolling at the school, Sunset Shimmer gives them a tour and informs them of an upcoming musical showcase. During the tour, Sunset gets a bad vibe from the girls, later noting "something off" about them to her friends. Not long after, the Dazzlings appear before the entire student body in the school cafeteria and convince them to turn the friendly competition into a Battle of the Bands. As a result, they turn everyone against each other, with the exception of Sunset and her friends, and even entrap Principal Celestia and Vice Principal Luna in the web of their spell.

It is later revealed through Twilight Sparkle's research that the Dazzlings are sirens from Equestria who long ago used their music to cause disharmony among ponies. Eventually, they were banished to the human world by Star Swirl the Bearded for their actions.

Throughout the competition, the Dazzlings draw the students and faculty in deeper with their siren songs and advance to the final round. They also convince Trixie to forcibly remove the Rainbooms from the competition by trapping them under a stage. Before the Dazzlings are able to grow powerful enough to rule the human world, the Rainbooms defeat them through the music of friendship and destroy their gem pendants, breaking their spell on the school and rendering them unable to sing.

The sirens are briefly mentioned by Pinkie Pie, Rarity, and Rainbow Dash. Pinkie recaps the events of the previous times they tangled with magic, including defeating the Dazzlings, after getting off the bus. During the campfire scene, Rarity and Rainbow also mention the sirens and the events of the second film.

Depiction in the series

In the season seven finale Shadow Play - Part 2, the sirens appear in flashback, creating discord among ponies with their singing before they were defeated by the Pillars of Old Equestria and banished to another world by Star Swirl the Bearded.

Other depictions

The Dazzlings, in their siren forms, appear in ancient Equestria in My Little Pony: FIENDship is Magic Issue #3. They enter a musical competition in Canterlot—from which they're initially ejected due to negative public reception. When they return after modernizing their singing, they captivate the ponies of Canterlot and draw the attention of Star Swirl the Bearded.

Through a series of musical battles, the sirens and Star Swirl create multiple new instruments and genres. After all of their battles end in Star Swirl's defeat, he banishes them to the human world through the Crystal Mirror.

In My Little Pony: Legends of Magic Issue #7, the Dazzlings appear before the unicorn Stygian and use their hypnotic singing to bring his village under their thrall. In Issue #12, the Pillars confront and banish the Dazzlings, despite Stygian's suggestion that they attempt to reason with the creatures.